The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
It is known to couple wave motion to an energy conversion device operable in response to wave motion, one example of which is use of a buoyant actuator to translate wave motion into a reciprocating action at the energy conversion device.
When exposed to an aggressive sea state, typically adverse weather conditions (such as in storm conditions), buoyant actuators can be subject to extreme forces. Known buoyant actuators can be prone to damage or detachment when exposed to such conditions. Further, systems and components to which the buoyant actuators are coupled can be subjected to excessive loadings. In the case of a wave energy conversion system incorporating such a buoyant actuator, various components (such as the pump, the foundation to which the pump is anchored, and the coupling between the buoyant actuator and the pump) can be subjected to excessive loadings.
There have been various proposals for relieving excessive loadings on the foundations, pump and coupling components in a wave energy conversion system for the purpose of avoiding damage thereof in adverse sea conditions. One such proposal involves selectively opening the interior of the buoyant actuator to permit water to flow through the buoyant actuator in response to exposure of the buoyant actuator to adverse weather conditions. Because water can pass through the interior of the buoyant actuator there is a reduction in resistance to the moving water that impinges on the buoyant actuator. This removes much of the potential energy, as the buoyant actuator is not being heaved as much by the waves. Further, it also reduces the kinetic energy at the same time because the susceptible mass is reduced (as water is no longer trapped within the buoyant actuator) and the velocity is reduced (because the buoyant actuator is no longer providing such reaction to the wave forces that would cause it to accelerate). In this way loading on the pump and associated coupling (including the tether) can be attenuated to an acceptable level and achieve this in an acceptably short period of time
It is against this background that the present invention has been developed.